Detect end of ScrollView

Question

I have an app, that has an Activity that uses a ScrollView. I need to detect when user gets to the bottom of the ScrollView. I did some googleing and I found this page where is explained. But, in the example, that guys extends ScrollView. As I said, I need to extend Activity.

So, I said "ok, let's try to make a custom class extending ScrollView, override the onScrollChanged() method, detect the end of the scroll, and act accordingly".

I did, but in this line:

scroll = (ScrollViewExt) findViewById(R.id.scrollView1); 

it throws a java.lang.ClassCastException. I changed the <ScrollView> tags in my XML but, obviously, it doesn't work. My questions are: Why, if ScrollViewExt extends ScrollView, throws to my face a ClassCastException? is there any way to detect end of scrolling without messing too much?

Thank you people.

EDIT: As promised, here is the piece of my XML that matters:

<ScrollView         android:id="@+id/scrollView1"         android:layout_width="match_parent"         android:layout_height="match_parent" >           <WebView             android:id="@+id/textterms"             android:layout_width="match_parent"             android:layout_height="match_parent"             android:gravity="center_horizontal"             android:textColor="@android:color/black" />      </ScrollView> 

I changed it from TextView to WebView to be able of justifying the text inside. What i want to achieve is the "Accept button doesn't activate until the terms of the contract are fully read" thing. My extended class is called ScrollViewExt. If i change the tag ScrollView for ScrollViewExt it throws an

android.view.InflateException: Binary XML file line #44: Error inflating class ScrollViewExt 

because it doesn't understand the tag ScrollViewEx. I don't think it has a solution...

Thanks for your answers!

Answer 1

Did it!

Aside of the fix Alexandre kindly provide me, I had to create an Interface:

public interface ScrollViewListener {     void onScrollChanged(ScrollViewExt scrollView,                           int x, int y, int oldx, int oldy); } 

Then, i had to override the OnScrollChanged method from ScrollView in my ScrollViewExt:

public class ScrollViewExt extends ScrollView {     private ScrollViewListener scrollViewListener = null;     public ScrollViewExt(Context context) {         super(context);     }      public ScrollViewExt(Context context, AttributeSet attrs, int defStyle) {         super(context, attrs, defStyle);     }      public ScrollViewExt(Context context, AttributeSet attrs) {         super(context, attrs);     }      public void setScrollViewListener(ScrollViewListener scrollViewListener) {         this.scrollViewListener = scrollViewListener;     }      @Override     protected void onScrollChanged(int l, int t, int oldl, int oldt) {         super.onScrollChanged(l, t, oldl, oldt);         if (scrollViewListener != null) {             scrollViewListener.onScrollChanged(this, l, t, oldl, oldt);         }     } } 

Now, as Alexandre said, put the package name in the XML tag (my fault), make my Activity class implement the interface created before, and then, put it all together:

scroll = (ScrollViewExt) findViewById(R.id.scrollView1); scroll.setScrollViewListener(this); 

And in the method OnScrollChanged, from the interface...

@Override public void onScrollChanged(ScrollViewExt scrollView, int x, int y, int oldx, int oldy) {     // We take the last son in the scrollview     View view = (View) scrollView.getChildAt(scrollView.getChildCount() - 1);     int diff = (view.getBottom() - (scrollView.getHeight() + scrollView.getScrollY()));      // if diff is zero, then the bottom has been reached     if (diff == 0) {         // do stuff     } } 

And it worked!

Thank you very much for your help, Alexandre!

Answer 2

I found a simple way to detect this :

   scrollView.getViewTreeObserver()        .addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {             @Override             public void onScrollChanged() {                 if (scrollView.getChildAt(0).getBottom()                      <= (scrollView.getHeight() + scrollView.getScrollY())) {                     //scroll view is at bottom                 } else {                     //scroll view is not at bottom                 }             }         }); 

• Doesn't need to custom ScrollView.
• Scrollview can host only one direct child, so scrollView.getChildAt(0) is okay.
• This solution is right even the height of direct child of scroll view is match_parent or wrap_content.